sound() is a duplicate of playsnd(). It should be removed

Reported by Samuel GOUGEON (@sgougeon)

BUG DESCRIPTION:
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sound() is a duplicate of playsnd(). It brings strictly nothing to playsnd(), that it wraps.
Any user can just set sound = playsnd to create an alias.
It should be removed from Scilab.


HOW TO REPRODUCE THE BUG:
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https://help.scilab.org/docs/6.0.2/en_US/sound.html
https://help.scilab.org/docs/6.0.2/en_US/playsnd.html


OTHER INFORMATION:
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Still in Scilab 6.0.2